1. Field of the Invention
The present invention relates to a dental abutment, which is fitted to the intraoral side of an implant fixture embedded in a jawbone and is fixed at the implant fixture with a bolt penetrating a through hole provided to be coaxial with a center axis. The dental abutment can strongly bond and fix a dental prosthesis, which is produced from cutting a ceramics block, to an accurate position based on three-dimensional shape data, (where the dental prosthesis includes members for a dental prosthesis, such as coping and the like).
2. Description of the Conventional Art
As a method of producing a lot of dental prostheses having stable quality for a short time as much as possible while reducing the burden to a dental technician, a dental CAD/CAM system has been developed in recent years. The dental CAD/CAM system is to produce a dental prosthesis by using a three-dimensional measuring apparatus, a computer or the like to create three-dimensional shape data of a dental prosthesis such as an inlay, a crown, a bridge, a coping, or the like, and cutting a block by an automatic cutting machine based on the three-dimensional shape data of the dental prosthesis.
When a dental prosthesis to be attached to the intraoral side of an implant fixture is produced by the dental CAD/CAM system, a different technique from an inlay or a crown is necessary. That is, the dental prosthesis for a dental implant is different from a dental prosthesis such as an inlay, a crown, or the like, and in the production of the dental prosthesis for a dental implant, it is necessary to produce a dental prosthesis capable of being strongly fixed at an accurate position of a dental abutment, so that the dental prosthesis can be placed and fixed at a position as planned, where the dental abutment is fitted to the intraoral side of an implant fixture embedded in a jawbone and fixed at the implant fixture with a bolt penetrating a through hole provided to be coaxial with a center axis.
A metallic dental prosthesis has been conventionally used as the dental prosthesis for a dental implant produced by the dental CAD/CAM system. Thus, since there is no problem in strength, the dental prosthesis is just produced to externally fitted to an accurate position of a dental abutment, which is fitted to the intraoral side of an implant fixture embedded in a jawbone and fixed at the implant fixture with a bolt penetrating a through hole provided to be coaxial with a center axis. However, in recent years, the dental prosthesis for a dental implant produced by the dental CAD/CAM system is made of ceramics such as zirconia or the like in recent years, so that the beauty appearance is not spoiled at a time of deterioration of gingiva after a dental implant treatment.
However, if ceramics such as zirconia or the like is used for a material of the block, the ceramics block is a sintered compact, and the degree of shrinkage generating after sintering is different in places, so that there is a problem that it is difficult to form the dental prosthesis to be externally fitted to the accurate position of the dental abutment after sintering. In addition, there is also a problem that the strength at a portion to be externally fitted to the dental abutment may be lacked in the ceramics dental prosthesis.
Present inventors have invested a method of producing a dental prosthesis to solve problems in the production of a dental prosthesis for a dental implant with the dental CAD/CAM system (refer to Japanese Patent Application Laid-Open No. 2007-222225). The method solves a problem that it is difficult to maintain a shape of a fitting part with desired dimensional accuracy after sintering of ceramics such as zirconia or the like, and a problem that the strength of the fitting part may be lacked in ceramics such as zirconia or the like. In the method, a separate part having a fitting part formed to be fitted to an implant fixture is produced in advance, and an embedding part of the separate part is embedded into an embedding hole and fixed, where the embedding hole is formed in advance at a block for a dental prosthesis or formed when cutting the block to be a dental prosthesis. Then, the fitting part to be fitted to the implant fixture is used in a state of projecting.
When the separate part is used, it is necessary to strongly fix the separate part to the block. For example, it is necessary to cut the separate part of a dental abutment or the like and an embedding hole formed at the block in advance or the like with high accuracy, insert an embedding part of the separate part of a dental abutment or the like into the embedding hole of the block, and strongly bond and fix the separate part with an dental adhesive or the like. The reason of this is as follows. That is, in case of the block made of ceramics such as zirconia, which has been widely used in recent years, the strength of the fitting part may be lacked. So, only by fitting a concave part provided at the embedding hole of the block to a projection part provided at the embedded part of the separate part of a dental abutment or the like, the block cannot be prevented from breaking in many cases.
In such a case of adhering and fixing, it is important that a gap for a dental adhesive is kept certainly between the embedding hole formed in the block and the embedded part of a dental abutment or the like, and that the embedded part of a dental abutment or the like is positioned and fixed in the embedding hole of the block. That is, since sufficient adhesive strength cannot be obtained if the coated dental adhesive is too thick, it is necessary to certainly form the gap so that the dental adhesive comes to be an uniformly desired thin layer. However, for example, only by cutting a cylindrical embedding hole and a columnar embedded part, coating an adhesive to an inner surface of the embedding hole and an outer peripheral surface of the embedded part, and inserting the embedded part into the embedding hole, the embedded part with a small diameter is freely moved in the embedding hole with a large diameter. Thus, it is very difficult to form a layer of the adhesive with an uniform thin thickness over an approximately entire circumference between the inner surface of the embedding hole and the outer peripheral surface of the embedded part. Therefore, it is necessary to enable to position and fix the embedded part of a dental abutment or the like in the embedding hole of the block.